Workers in high temperature environments customarily wear some form of micro-climate control system, which serves to remove metabolic heat from a person's body and thereby enables the worker to operate within the environment for reasonably lengthy periods of time (several hours). In order to not unduly limit the wearer's movement, vest-configured temperature control systems are considered to be one of the more practical approaches to sustained body control. One of the more common vest designs contains small diameter plumbing lines, embedded into the fabric of the vest, through which cold water is pumped. The body heat which is removed (transferred into the cooling water) is drawn off by a heat exchange device (usually a substantial reservoir of ice), which may be carried by the worker (e.g. by hand or via a backpack). A principal drawback to this type of cooling system is the fact that the cooling water is considerably colder (often 40.degree. or more colder) than the desired skin temperature, which causes an undue and uncomfortable cooling of different parts of the body. To resolve this problem it becomes necessary to incorporate a control device into the cooling system, so as to shut off or vary the proportion of cooling water flow to various parts of the body. Unfortunately, this solution adds further weight, complexity and reliability problems to a system that is already burdened by a heat exchanger, pump (to circulate the water) and battery (to power the system).
Another, but less used, design employs a pressurized fluid stored in a pressure vessel, which is flashed-off to provide the requisite cooling. In addition to the weight of the pressure vessel, such a system suffers from the greater problem of environmental air contamination. Usually this type of system utilizes fluorocarbon refrigerants which are flashed and then expelled into the atmosphere where the worker is located. To obviate this problem liquid air ca be flashed off to provide both a cooling source and breathing air. However, like the configuration described supra, the system is complex, heavy and operates at temperatures well below a desired skin-surface temperature of 80.degree.-90.degree. F. (For an illustration of Patent literature describing personal cooling systems of the types described above, attention may be directed to the U.S. Pat. Nos. to Friedlander et al 3,643,463, Konz et al 3,950,789, Rowe 3,802,215, Gough 3,296,819, Troyer 3,610,323 and Elkins et al 4,691,762.)